A metal loop with a spring-loaded gate used to connect safety-critical components. Short for Karabinerhaken which means "spring hook" in German. Definition from Carabiner article on Wikipedia.
Same as Biner.
Some of the parts here are specific to HMS carabiners and I am using names I have heard in canyoneering.
The versatile end that holds the devices that do things - devices such as ascenders, rappel devices, friction hitches, safety tethers, or a munter hitch. I've also heard it called Basket and Wide End.
The end that attaches to a single point such as the anchor or a rappeller. Also called the Runner End.
The opening part of the carabiner beyond the hinge.
The tip of the carabiner that touches the gate when closed.
The direction a carabiner is designed to be weighted.
The direction that cross-loads a carabiner.
There are actually many types of carabiners for with specialized uses, but I'll just go over three climbing-specific types.
The original carabiner shape. This carabiner balances the load on both the strong spine and the weak gate which results in a somewhat heavier carabiner to obtain adequate strength. However, the wide basket and symmetrical shape provide some advantages.
This shape attemps to remove the principle disadvantage of the Oval shape by positioning the load onto the spine of the carabiner. This results in the lightest shaped carabiner but also makes it the least versatile.
The HMS carabiner was designed for the Munter Hitch and is inherently the most versatile carabiner and the preferred shape of most canyoneering carabiners. Much more on this shape in the rest of the article.
Carabiners must be strong enough to withstand the extreme forces placed upon it by canyoneers. If it doesn't have a valid climbing certification it should not be used. All carabiners I use have a CE marking and show the minimum breaking strength on the major axis, minor axis, and with an open gate. If the carabiner says SWL (Safe Working Load) or "NOT FOR CLIMBING" then it is not certified for climbing and should not be used. See this excellent blog post from Weigh My Rack for more information on carabiner strength.
Minimum Breaking Strength
The minimum amount of force required that could cause a safety-critical component to fail.
Same as MBS.
Carabiners used for canyoneering have a minimum breaking strength rating printed or forged somewhere on the carabiner for at least the major axis, minor axis, and with an open gate.
The above definition entails many types that do not work for canyoneering. Let's briefly talk about these types and why they should not be used.
Carabiners with non-locking gates are are typically used as part of a climbing quickdraw. Their purpose is to allow a climber to quickly clip into the rope with one hand and continue up a pitch. There is no practical application for a non-locking carabiner in canyoneering and these types of carabiners should be left at home.
The one exception to this is using two non-locking carabiners in place of a single locking carabiner. The carabiners must be oriented opposite of each other so that when the gates open it forms an X.
Auto locking gates require that the internal mechanisms be clean to operate properly. Since canyoneering is a dirty, nasty, filthy affair and carabiners often get dragged through dirt and mud, auto lockers generally don't have a place in canyoneering, either.
Other problems with auto lockers are that they are generally more expensive than the screw gate versions. They are also often a little heavier. They are more fragile - their locking mechanisms can break more easily if dropped. Finally, the locking mechanisms aren't necessarily intuitive. You can't hand one to another canyoneer and expect them to know how to use it. Passing a screw gate is always a better idea.
The one place I still see auto lockers used is the carabiner attached to a canyoneer's rappel device. Since these carabiners will never be used for rigging or in a biner block, they won't necessarily get dirty every time they are used. I personally do not subscribe to this method but as long as the canyoneer who uses auto lockers is aware that they need to keep it clean then I don't care.
Aluminum is significantly lighter than a similar steel carabiner. For example, the very-light-for-being-steel carabiner I use weighs 190 grams and the aluminum carabiners I bring with me weigh 80 grams. That means I could carry two aluminum carabiners and still bring less weight than a single steel biner.
The principle advantage of steel carabiners for canyoneering are that they are much more durable than aluminum carabiners. I have seen aluminum carabiners wear out in just one canyon. Before getting my steel carabiner I had to inspect my aluminum wear points after every canyon. The steel one should last me years.
Other less important differences are that aluminum carabiners are generally less expensive and steel carabiners have a much greater minimum breaking strength.
Beam shape is the term I use to describe the cross-section of the carabiner shaft. The original carabiners were all round or convex. However, much of the aluminum material doesn't actually add strength to the carabiner and is basically just useless additional weight. I call carabiners that are shaped in a way that do not include this additional material concave. I've also heard it referred to as I Beam or H Beam but there are many other variations.
As stated above, concave carabiners weight less than their convex counterparts. That's their one advantage. They are also slowly phasing out many of the older convex shapes in higher-end carabiners.
The principle advantage of convex carabiners are that they wear out more evenly and provide more consistent friction when on rappel. They are also cheaper to manufacturer and that savings is passed onto the purchaser
The original nose type looks like a hook where the gate rests. These hooks tend to catch on gear when pulling it off of the carabiner.
Most new carabiners feature a "keylock" nose that eliminates the need for a hook by having the gate pinch the nose instead of hook into it. This nose is apparently a little more expensive to manufacture.
A few carabiner gates don't open inline with the rest of the carabiner. The open at a slight angle that allows the gate to open slightly more before touching the spine.
I have a harness that I used for years. When I first got the harness I discovered that my Petzl Attaches couldn't clip into the gear loops very easily. I ended up switching from Attaches to Rock Exotica Pirates. Even though the carabiners where nearly the same size, the Pirates had an angled gate opening that allowed them to open just a bit more and easily clip into the wide gear loops.
In general, larger carabiners are more useful than small carabiners. Advantages of each as follows.
Small carabiners are a little lighter and less expensive. There you go - those are the advantages.
Large carabiners won't fit through the largest rapides like small carabiners can. They are also much easier to connect things to since they have a wider opening. I've struggles with getting block hitches off of small carabiners because of the small gate opening and small area to "break" the tightened hitch. I definitely have a bias toward larger carabiners.
The preferred carabiner shape for canyoneering is the HMS carabiner shape due to its versatility. There are very few things an HMS carabiner cannot do that other carabiners can do better.
The one big exception to this is the carabiner used for a Tibloc. It should use an Oval carabiner. Petzl says the following in regards to the Tibloc:
Can I use a TIBLOC with an ATTACHE 3D carabiner?
Carabiner shape and cross-section play a significant role in the jamming of the rope. For optimal operation, a carabiner with round cross section is preferable.
If I were to buy only one type of carabiner for canyoneering it would be large, aluminum, HMS, screw gate, key-lock, with a convex beam. This is the type of carabiner I buy most of the time. There are places where other carabiners work better, but this type of carabiner works well enough in every canyoneering application I have experienced so far.
As a matter of fact, I used this type of carabiner exclusively in canyons for years without ever being questioned on it or giving it a second thought.
If I were to buy 2 types of carabiners I'd get a steel carabiner for my rappel device. Or some larger carabiners like the Petzl William or Sterling Eagle. Or Some smaller ones that I don't cry about when I loan them out and they never get returned. I don't know.
There is no way to mark carabiners and have the marking last. Lots of people use tape on various locations. Lots of people, myself included, use nail polish. I chose to put nail polish near the gate hinge because that seemed like the place that would last the longest. I have found that if I mark them once a year it works well enough. You can see the "before" and "after one year" in the above image.
Wash carabiners with water and optionally mild soap. I rinse my carabiners under the faucet and have never used soap. If sand gets in the screw gate I screw and unscrew it while under the faucet and the sand works itself out.
You can lubricate the spring with oil. I have heard you can use graphite to lubricate the screw but have never tried it or confirmed it with any manufacturer. Don't use WD 40.
Unlike plastic products, there is no end-of-life for metal carabiners. However, if at any point you do not feel 100% confident in the carabiner then it should be retired. The most common reason for me to retire a carabiner is when the working end gets worn out from rappelling.
I occasionally find previous party's carabiners while canyoneering and never use them because I do not feel 100% confident and am not familiar with where it has been.
If you drop it can you still use it? I don't know. I'm not an authority on any of this. This is all just medium quality canyoneering information.
One last note - all images of clean carabiners are from their respective manufacturers. All images of scratched up carabiners are mine.